to an observer the pitch of the stationary source of the sound appears to be reduced by 20% if speed of sound is 340m/s then sped and direction of 5he observer is
1.68 m/s away from the observer
2.96 m/s away from the observer

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  1. {f(observed) - f(source)}/f(observed) = 20/100, u = 340 m/s
    At source approaching
    f(observed) = [v/(v-u)] •f(source),
    v =[f(obs)-f(sour)] •u/ f(obs) = 20% •340/100%= 68 m/s.

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